A typical radio communication system includes a plurality of multiple switching centers, a plurality of base stations, and a plurality of mobile stations. The multiple switching centers connect the radio communication system to the public switched telephone network. The base stations are connected to the multiple switching centers by in ground cables or by wireless techniques such as Ericsson Mini Link, a registered trademark of Ericsson. Each base station controls the radio communications within certain areas which are called cells. A mobile station operating in a particular cell communicates with the base station for that particular cell through open air transmissions.
When a new cellular system is being set up or during maintenance of an existing system, it may be necessary to perform repeated tests on the system since potential faults or problems may not be detected by a single test. In addition, the reliability of the system and the controlling software can also be verified by using repeat testing. In particular, it may be necessary to perform repeated tests on the radio path between base stations and mobile stations. Several methods for testing the radio paths between radio base stations and mobile stations have been suggested. In particular, methods have been suggested in which tests are performed in the actual site environments and also methods that simulate a cellular system.
The prior test methods which conduct measurements in the actual site environment use actual base stations and actual mobile stations during the test which communicate using open air transmissions. For example, the tests can be performed on the radio paths between a base station and several mobile stations which are placed at various locations in the radio communication system. Tests are then run on the radio path between the individual mobile stations and the base stations and the results of the tests are recorded at the base stations and the mobile stations. However, it is hard to compare the results obtained from repeated tests since the testing conditions in these open air environment systems are always changing. In these open air environment systems, weather changes, interfering signals, rayleigh fading conditions all vary with time and therefore it is difficult to conduct repeated testing since the testing conditions are always changing.
Other existing radio environment networks which simulates open air environment systems are well known in the art. In these systems a base station and a mobile station are connected by a cable through which they communicate with each other. These networks use the same radio path for sending signals between the base stations and the mobile stations. While such systems do not have the problems that are associated with the open air environment systems, i.e., conditions which vary during the repeated tests, these systems have several disadvantages. For instance, since these systems use the same radio path for sending signals back and forth between the base stations and the mobile stations, frequency intermodulation and signal reflections are introduced into the system.
Therefore there is a need for a system which simulates a cellular system wherein repeated tests can be performed under constant testing conditions without introducing frequency modulation and signal reflections into the tested system.